Purification of glyceride oils



B. CLAYTON PURIFICATION OF GLYCERIDE OILS July 7, 1953 Re. 23,680

Original Filed April 21. 1943 .54 a J/ J x dz Jnmcwtom flezykzminC'layiwz lax-2A4, 95,611 4m 3. WOT/P141146 seamed July 7, 1953PURIFICATION OF GLYCERIDE OILS BenJamin Clayton, Pasadena, Calii'.,assignor, by mesne assignments, to Benjamin Clayton, doing business asRefining, Unincorporated Original No. 2,412,251, dated December 10,1946, Serial No. 483,953, April 21, 1943. Application for reissueOctober 7, 1952, Serial No. 313,620

23 Claims. (Cl. 260-425) Matter enclosed in heavy brackets II appears inthe original patent but forms no part of this reissue specification;matter printed in italics indicates the additions made by reissue.

This invention relates to the purification of oil and more particularlyto a process for the re-' moval of small amounts of impurities fromglyceride oils, such as animal and vegetable oils, which oils aresubstantially free of fatty acids and gums.

It is frequently necessary to purify glyceride oils which are low infree fatty acid content, for example, oils having free fatty acidcontent below 25% and which are also low in materials commonly referredto as gums, namely, phosphatides, proteinaceous materials; resins, etc.vThe impurities required to" be removed may be coloring matter ormaterials which impart to the oil a deleterious taste or odor. Or it maybe desired to treat an oil which has naturally occurring impurities invery limited quantities.

-An example of a glyceride oil which requires color removal is acottonseed oil which has been refined with non-saponifying alkalies suchas soda ash or has been refined with insufficient caustic alkali tolower the color of the oil to the required extent. The employment ofnon-caustic alkali adequately removes the free fatty acid content andalso removes substantially all of the shins but the resulting oil isusually of darker color than that desired. The losses resulting from therefining of vegetable oils in a continuous process using soda ash orother non-saponifying alkalies are much less than in processes in whichsi'iificient caustic alkali is employed in the first instance to notonly remove fatty acids and gums from the oil but to produce a lowcolored. oil. It is. however, necessary to re-refine the oil using acaustic alkali or similar color reducing material to produce a lowcolored oil.

Cottonseed oils vary widely in their characteristics from year to yearand in accordance with production areas. It has been found possible tore-refine certain types of cottonseed oil, after they have been refinedby a continuous soda ash process, by using small amounts of relativelydilute caustic alkali in a continuous process to obtain a properlydesolorized oil with exceedingly small losses. However, it has also beenfound that many and perhaps most cottonseed oils, are not capable ofbeing re-refined with small amounts of relatively dilute caustic alkali.Such dilute alkali not only fails to reduce the color of the oil butproduces difficultly separable emulsions which are not properlyseparated in a continuous centrifugal separator.

In accordance with the present invention, it has been found thatemulsion difliculties may be obviated and an adequate reduction of thecolor 2 of the oil can be obtained by employing small amounts ofrelatively concentrated caustic soda, for example, concentrationsbetween 20 and 50 Baum. The use of, such concentrated solutions,however, has heretofore been found impossible in continuous refining asstrong caustic solutions cause the small amount of soap formed duringthe re-refining operation to be salted out of the caustic solution andto separate with the neutral oil in the centrifugal separator. Byemploying a strong caustic solution for color removal and then dilutingthe caustic-immediately before or during separation of the oil from thedecolorizing reagent, soap and precipitated impurities, it has beenfound that the beneficial effects of the strong caustic solution can beobtained while separation difiiculties are obviated. Diificultiessimilar to those described above are encountered with various other oilswhich are low in free fatty acid and gum content and the employment ofstrong caustic solutions to precipitate or remove impurities from theoil, followed by dilution of the caustic solution during or just priorto separation, has also been found applicable in the treatment of suchoils. I

It is therefore an object of the present inven tion to provide animproved process for removing impurities from glyceride oils which arelow in free fatty acid and gum content.

Another object of the invention is to provide an improved process ofremoving small amounts of impurities from glyceride oils having low freefatty acid and gum content in which process strong caustic alkalisolutions are employed but are diluted prior to the separationoperation.

Another object of the invention is to provide a process of re-refiningglyceride oils containing only a small amount of impurities in whichrefining losses are reduced.

A further object of the invention is to provide an improved processofeilectively remov ing impurities from glyceride oils which contain smallamounts only of such impurities so as to overcome separationdifiiculties.

A still further object of the invention is to provide an improvedprocess of reducing the color of refined glyceride oils by chemicaltreatmentand with substantially no refining losses.

Other objects and advantages of the invention will appear in thefollowing description of preferred embodiments thereof given withreference to the attached drawing in which:

Fig. l is a schematic diagram of an apparatus suitable for carrying outthe present invention, and

i l 'ig. 2 is-a somewhat tic vertical sectional view through acentrifugal separator bowl,

particularly applicable for use in the present invention.

Referring to Fig. l, the process of the present invention is preferablycarried out in apparatus in which an oil is treated with a reagent forprep cipitating the impurities and then delivered into a centrifugalseparator I. for separation ofthe precipitated material or foots fromthe oil. The

.miltobetreatedmaybewithdrawnfromasourw 'ofsupplysh'ownasatankilbymeansofaproportioning pump it and delivered through a heatingcoilllofaheat exchange device lltoamixer II. The tank may be provided with aheating coil ll orsimilarheatingmeansformaintaining the oil in the tankii in'iiuid condition in case oils or fats solid at ordinarytemperatures are being treated. The reagent for precipitating impatentto Thurman 2,142,062 granted December .27. 1938. v

A thorough mixtureof the reagent and oil produced in the mixer II isthen passed through a heating coil ll of the heat exchanger 24 anddelivered into the centrifugal "through the pipe 28. A diluting agentfor thereagent in the mixture entering the centrifugal it may bewithdrawn from tank 21 by means of a proportioning pump ll and deliveredthrough the coil II of the heat exchanger Ii and a pipe 32 so as to beadmixed with the oil reagent mixture at the entrance of the centrifugalseparator II. The diluting agent which, in most instances, is water,

dilutes the mixture so that soap formed in the reaction is retained insolution in the aqueous phase or heavy eiiiuent and discharged throughthe spout it into a receiver it while the purified oil is dischargedthrough a spout it into a receiver 31. The proportioning pumps I2, I!and It may be drivenby a variable speed electric motor is connecteddirectly to the oil pump it and through variable speed devices II andbe-- tween the motor 18 and the proportioning pumps is and II,respectively. Other types of proportioning apparatus may, however, beemployed, for example, that shown in patent to Thurman above referred.

Instead of delivering the diluting agent into the oil-reagent mixture asthe mixture enters the centrifugal separator, it is preferred to admitthe diluting agent with the heavy eiiiuent in the centrifugal afterseparation has been largely accomplished. This avoids substantially allcontact between the oil and a dilute reagent so that emulsion.difiiculties are entirely overcome. A suitable type of centrifugalseparator for accomplishing this operation is shown in Fig. 2. Such aseparator may include a bowl 42 mounted upon a shaft 43 for rotation athigh speed and may and outwardly into the lower portionof the bowl. Theseparation none of the bowl may be provided with a plurality of conicalbaiiie members II which are apertured at I! adjacent the neutral zone ofseparation. Material to be separated fiows upwardly through theapertures II, the light eiliuent comprising the oil flowing inwardly inthe bowl and being discharged through the outlet port II. The heaviermaterials comprising to the lower periphery of the bowl. The dilutingagent admixes with the heavy eiiluent to dilute the same and cause anysoap present in the mixture to be retained in solution or dissolved inthe I heavy eiiluent so as to be discharged therewith 1 through the portll.

In treatment of oils such as those contemplated in the presentinvention, namely, oils which are low in free fatty acid and gumcontent, the heavy efiiuent is predominantly an aqueous solution of thereagent even before dilution with the diluting agent. This aqueoussolution contains excess reagent and small amounts of soap. Attempts toemploy dilute precipitating agents result not only in ineffectiveremoval of impurities from the oil but in the formation 'of tightemulsions which,

heavy effluent through the port ll, resulting in high refininglosses. Inmany instances also the iilrlipurities are not adequately removed fromthe o .By employing strong precipitating reagents such as caustic sodasolutions ranging between 20to 50 Baum, such emulsions are notencountered and in accordance with the present inven- ,tion refininglosses are reduced to avery low also include an outlet port M for thelight eiliuent and an outlet 48 for the heavy eifiuent. The oil andreagent mixture containing precipitated impurities, as well as a smallamount of soap, is delivered into the centrifugal through a stationarypipe 41 and then delivered into a tubular inner bowl member 48 by meansof a distributor II. The inner bowl member I. divides the separationzone of the bowl from the inlet portion thereof and directs the incomingmixture downward y.

- v This difiiculty can be overcome by diluting the I figure. However,small amounts of soap are formed by reaction of thecaustic alkali withresidual free fatty acids in the oil or by reaction with the oil itselfand this soap is grained out of the heavy eiiluent in the centrifugal.Three layers of strata tend to be built up in the centrifugal bowl: aninner oil layer, an intermediate soap layer, and an outer aqueous layer.These layers are not definitely defined and any attempt to adjust thecentrifugal to separate the soap with the aqueous layer causes highrefining losses whereas failure to separate the soap with the aqueouslayer produces an impure oil requiring extensive further purificationtreatment.

mixture just prior to centrifugal separation, for example,by'introduc'ing a diluting agent such as water into the mixture enteringthe centrifugal but a slight amount of difiicultly separable emulsionmay be formed due to contact betwee the oil and diluted reagent and itis found that the precipitation of impurities such as coloring matter isnot as effective as is the case when separation is substantiallycomplete prior to dilution of the mixture. In the centrifugal separatorshown in Fig. 2, diluting of the heavy efliuent after complete orsubstantially complete separation thereof from the oil causes the soaplayer above referred to, to remain in solution or go into solution inthe aqueous layer so that it separates cleanly from the oil.

Reaction of color impurities, with a precipitatin'g reagent such ascaustic soda usually takes place more rapidly and more completely at lowtemperatures, for example, temperatures between 70 and 100 F. The oil inthe tank ll of Fig. 1 is therefore preferably maintained between thesetemperatures except in cases where the oil is delivered to the tankfroma prior refining or similar process at a high temperature or the oil orfat requires heating to a higher temperature to render the same fluid.The heat exchanger I4 is therefore not employed when the oil is at thecorrect temperature for admixture with the precipitating reagent but maybe employed to either cool or heat the oil in In general the temperatureof the re-' reagent are thus delivered to the mixer l5 by perature ofthe mixture to that required for effective centrifugal separation. Thesetemperatures willusually range between 120 and 180 F., depending uponthe type of oil being treated, the impurities desired to be removed and.the melting temperature of the oil. The oils being treated willordinarily contain not more than approximately 25% free fatty acid andonly slight amounts or traces of gums. The preferred reagent is aconcentrated aqueous solution of caustic soda, for example, solutionsrang ing from 20 Baum up to Baum. A conslderable excess of caustic sodaover that required to neutralize any free fatty acids present is usuallyemployed. Thus the amounts of caustic solution will usually rangebetween approximately and 4%, the quantity most generally used being inthe neighborhood of 2%.

As stated above, the temperature of mixing is preferably between and F.although for removing certain types of impurities this temperature maybe as high as to F. The temperature of separation will, however, usuallyrange between 120 and F., although this temperature may at times be aslow as 100 F.

Water is the preferred diluting agent and the amount of water willordinarily range between approximately- 2.5 and ten times the amount ofreagent employed. In general, it has been found desirable to reduce theconcentration of the excess reagent in the centrifugal to at least 8Baum although in some instances higher concentrations up to 10 or 12Baum have been found operable and lower concentrations ranging down toapproximately 4" Baum may sometimes be found advantageous in thecentrifugal separator. In any event, the amount of. water or otherdiluting agent employed in the centrifugal separator should besufficient to cause the soap to separate in solution or in dispersedform in the aqueous phase. Also the temperature of the diluting agentshould in general, be at least as high as the temperature of separationand preferably is somewhat higher. Thus the temperature of the dilutingagent will range between approximately 100 and 200 F. I

, The material discharged from the centrifuge is in most cases largelywater contaihinmexcess caustic soda and a small amount of soap. Ingeneral the amount of soap will not exceed 2% and is usually between 2%and 1% of the material discharged. By employing strong'caustic alkalisolutions and diluting the same just prior to or during separation, thelosses rarely exceed .2% and usually do not exceed .15% whereas thelosses when employing equivalent amounts of dilute caustic soda in thefirst instance may run as'high as 2% or higher. It has been found thateven increasing the amount of 'caustic solution does not measurablyincrease the losses in the process provided suillcient diluting agentis'introduced to carry the concentrationof the reagent in thecentrifugal below that at which soap tends to separate with the oil.

While the present process is particularly adaptable to the re-reflningof cottonseed oil: previously refined by a continuous soda ash process,such as oil refined by the processes disclosed in my Patents No.2,249,701, and No. 2,249,702, granted July 15, 1941, certain vegetableor animal oils in the form they are recovered from the raw material arenaturally low in free fatty acids and gums and the present process maybe advantageously employed for removal of small amounts of impuritiestherefrom. Also substantially completely refined oils intended foredible purposes are frequently processed under conditions which somewhatincrease their free fatty acid content and impart deleterious tastes orodors thereto. Such oils or fats are advantageously subjected to theprocess of the present invention Sfor removal of the small amounts ofimpurities contained therein. Furthermore, certain light colored oils,such as-corn oil, requiring no treatment for color reduction afterrefining in continuous soda ash processes, are benefited by treatment inaccordance with the present invention as in some instances such oils areextremely difiicult to'wash without excessive refining losses. It hasbeen found that treatment in accordance with present invention, it isalso possible to employ sodium peroxide which liberates caustic sodawhile admixed with water and should be used in sufficient amounts toproduce the concentration of caustic soda contemplated in the. presentinvention. The sodium peroxide additionally liberates oxygen whichmaterially assists in removing coloring matter and other impurities fromthe oil. An advantageous operation is to employ a reagent consistingpredominantly of caustic soda-but containing a small amount of -so dium'peroxide or other oxygen liberating material. Other equivalent alkalimetal compounds such as potassium compounds are also suitable.

This application is an application for reissue of my Patent No.2,412,251, granted December 10, 1946 on an application Serial No.483,953 filed April 21, 1943 which application is a continuation-in-partof my copending application Serial No. 398,480, filed June 17, 1941,which is in turn a division of Serial No. 296,885, filed September 26,1939, nowvPatent No. 2,249,701, granted July 15, 1941.

While I have disclosed the preferred embodiment of my invention, it isunderstood that the details thereof may be varied within the scope ofthe following claims.

I claim:

l. Theprocess of purifying a glyceride oil which is low in free fattyacid and gum content and contains small amounts of other impurities,which process comprises, ixin with said all a caustic soda solutionhaving a concentration between approximately 20 and 50 as, said reagentbeing added in suflicient amount to precipitate said impurities andprevent the formation of an emulsion in said oil and'said reagent,whereby the resulting mixture will separate into an oil layer, a soaplayer, and anaqueous layer containing said impurities when subjected tocentrifugal separation, subjecting the resulting mixture to centrifugalseparation and diluting said mixture prior to complete separation in thecentrifugal to lower of the concentration of the aqueous layer tobetween appl'oximately i and 86., whereby said soap discharges with saidaqueous layer from said centrifugal.

2. The process of purifying a glyceride oil which is low in free fattyacid and gum content and 4. The process of purifyinga glyceride oilwhich is low in free fatty acid and gum content and contains smallamounts of other impurities, which process mixing with said 011 acaustic alkali solution having a concentration between approximately and50 .se. to precipitate said impurities and form a small amount of soap,

" aqueous phase and said soap have been at least partially separatedfrom said oil. to reduce the concentration of said aqueous phase to atleast 8" B6. whereby said soap discharges from said centrifugal withsaid-aqueous phase.

.' 5. The process of purifyins a glyceride oil which is low in freefatty acids and gumcontent.

- which process comprises mixing with said all a proximately 20 and B.,said reagent being added in 'suflicient amount to precipitate saidimpurities and prevent the formation of an emulsion of said oil and saidreagent, whereby the resulting mixture will'separate into an oil layer,a soap layer, and an aqueous layer containing said impurities whensubjected to centrifugal separation, subjecting the resulting mixture tocentrifugal separation and diluting said reagent prior to completeseparation in the centrifugal so as to produce a concentration in saidaqueous layer not substantially greater than 8 36., whereby said soapdischarges with said aqueous layer from said centrifugal.

3, The process of purifying a glyceride oil which is low in free fattyacid and gum content and contains small amounts of other. impurities;which process'comprises, mixing with said oil a caustic alkali solutionhaving a concentration between approximately 20 and 50 B. to precipitatesaid approximately 4 and 10 B. whereby said soapdischarges from saidcentrifugal with said aqueous phase.

caustic alkali solution having a concentration between approximately 20and 50 as. to precipitate said impurities and to form a small amount ofsoap, and of suiiicient concentration to stratify the mixture into anoil phase, a soap phase and an aqueous phase when the same is subjectedto centrifugal separation, thus interferwith such separation, subjectingthe resulting duced to between approximately 4 and 10 36.

-'l. The process of purifying vegetable and ani- -mal oils containingimpurities, including free fatty acids, which comprises, mixingtherewith an alkaline refining reagent capable of reacting with saidimpurities to precipitate the same and produce soap, said reagent beingadded in sufiiciently high concentration to produces. stratifled mixtureincluding an oil phase, a soap phase, and an'a'queous phase when themixture is subjected to centrifugal separation, thus interfering withsaid separation, reducing concentration by adding an aqueous diluent tosaid mixture in sufflcient quantity to overcome such stratiflcation.whereby to permit said soap to be discharged with said aqueous layer,and centrifugally separating the thus conditioned mixture.

8. Theprocess as defined in claim 7 in which the dilution'produces aseparation of the heavier efliuent having a Baum between approximately 4and 10.

9'. The process as defined in claim 7 in which the dilution is effectedafter the soap has been at least partially separated from the chin thecentrifugal apparatus.

-- 10. The process as defined in claim 7 in which the dilution occursprior tocompleteseparation in the centrifugal.

11. The process as defined in claim 7 in which the impurities separatedfrom the oil in the centrifugal are diluted in the centrifugal aftersubstanthl-separation from the oil.

. 12. A re-reiining process for oils of low impurity content whichprocess comprises the treat-' aqueous phase when the mixture issubjected to centrifugal separation. introducing water to laid mixture"in sumcient quantity to convert the mixture from its thus stratifledcondition to a lullciently non-stratifled condition to permit thesoapstock to be discharged with the aqueous phase, and cen-triiugallyseparating the thus conditioned mixture.

13. The process as defined in claim 12 in which the water is introducedat the point of separation in the centrifugal.

14. The process as defined in claim 7 in which the mixture beingseparated is at a temperature in excess of 100 F.

j 15. The process as defined in claim 7 in which theoil is at arelatively low temperature when mixed with the refining reagent andprior *to separation the temperature of the mixture is raised to thatrequired for eflective centrifugal separation.

16. The process as defined in claim 7 in which the amount of alkalirefining reagent is between approximately 55 and 4% of the oil.

17. The process as defined in claim 7 in which gum content of the oil issuihciently low to cause separation d iflculties.

18. The process as defined in claim 7 in which the gum content of theOil is sufllciently low to cause separation dimculties, the temperatureof the mixture being separated is in excess of 100 F, and sufficientlyhigh for eflective centrifugal separation and the quantity of aqueousdiluent is sufficient to reduce the concentration of the excess refiningreagent in the separated aqueous layer to at least 8' Bawme.

19. The process as defined in claim 7 in which the refining reagent hasa concentration between approximately 20"v and 50 Baume.

V10 20. The process as defined in claim 19 in which the quantity ofaqueous diluent is suihcient to reduce the concentration of theseparated aqueous layer to between approximately 4 and 10 Baume.

21. The P ocess as defined in claim 19 in which the amount of aqueousdiluent is sumcient to cause the aqueous lailer discharged from thecentrifugal separation to be largely water.

22. The process of purifying vegetable and animal oils, low in gumcontent and containing im-' purities, including free fatty acids, whichcomprises, mixing therewith an alkaline refining reagent capable ofreacting with said impurities to precipitate the same and produce soap,said reagent being added in sufliciently high concentration to produce astratified mixture including an oil phase, soap phase, and an aqueousphase when the mixture is subjected to centrifugal separation, thusinterfering with said separation, reducing concentration by adding anaqueou diluent to said mixture in sufilcient quantity to overcome suchstratification, said quantity of aqueous diluent reducing theconcentration of the excess of alkaline reagent to at least 8 Baume,whereby to permit said soap to be discharged with said aqueous layer,and centrifugally separating the thus conditioned mixture.

23. The process as defined in claim 22, in which the temperature of theconditioned mixture during centrifugal separation is in excess of 100 F.

BENJADAIN CLAYTON.

UNITED STATES PATENTS Name Date Thurman Dec. 24, 1940 patent Number

